Group of syndromes phenotypically related to Noonan syndrome and characterized by a genetic abnormality of the RAS/MAPK cellular signaling pathway. This pathway transduces the extracellular messages produced by small molecules to the cytosol and nucleus. Multiple proteins are involved in this process and many mutations are therefore involved.

Variable association of heart disease, facial dysmorphism, skin abnormalities, intellectual difficulties and a propensity to develop benign or malignant tumors.

The syndromes of this group are:

-        Noonan syndrome

-        Costello syndrome

-        cardio-facio-cutaneous syndrome

-        Legius syndrome

-        LEOPARD syndrome which was renamed Noonan syndrome with multiple lentiginoses

-        CBL syndrome

-        Noonan-NF1 syndrome

-        Noonan syndrome with fragile anagen hair

References : 

-        Verloes A, Cave H. 
Syndrome de Noonan et RASopathies apparentées, 
In Syndromes dysmorphiques, édité par D Lacombe et N Philip, Série Progrès en Pédiatrie, Doin 2013, p 13-26.

Updated: October 2018